Buggy code:
protected String routerField ; protected Integer numShards ; protected Integer maxShardsPerNode ; protected Integer replicationFactor ; public Create ( ) { } public void setConfigName ( String config ) { } public void setCreateNodeSet ( String nodeSet ) { } public void setRouterName ( String routerName ) { } public void setShards ( String shards ) { } public void setRouterField ( String routerField ) { } public void setNumShards ( Integer numShards ) { } public void setMaxShardsPerNode ( Integer numShards ) { } public void setReplicationFactor ( Integer repl ) { } public String getConfigName ( ) { } public String getCreateNodeSet ( ) { } public String getRouterName ( ) { } public String getShards ( ) { } public Integer getNumShards ( ) { } public Integer getMaxShardsPerNode ( ) { } public Integer getReplicationFactor ( ) { } @ Override public SolrParams getParams ( ) { ModifiableSolrParams params = ( ( ModifiableSolrParams ) ( super . getParams ( ) ) ) ; if ( ( configName ) != null ) { params . set ( "collection.configName" , configName ) ; } if ( ( createNodeSet ) != null ) { params . set ( "createNodeSet" , createNodeSet ) ; } if ( ( numShards ) != null ) { params . set ( NUM_SHARDS_PROP , numShards ) ; } if ( ( maxShardsPerNode ) != null ) { params . set ( "maxShardsPerNode" , maxShardsPerNode ) ; } if ( ( routerName ) != null ) { params . set ( "router.name" , routerName ) ; } if ( ( shards ) != null ) { params . set ( "shards" , shards ) ; } if ( ( routerField ) != null ) { params . set ( "router.field" , routerField ) ; } if ( ( replicationFactor ) != null ) { params . set ( "replicationFactor" , replicationFactor ) ; } return params ; } } public static class Reload extends CollectionAdminRequest { public Reload ( ) { } } public static class Delete extends CollectionAdminRequest { public Delete ( ) { } } public static class CreateShard extends CollectionAdminRequest . CollectionShardAdminRequest { protected String nodeSet ; public void setNodeSet ( String nodeSet ) { } public String getNodeSet ( ) { } public CreateShard ( ) { } @ Override public SolrParams getParams ( ) { ModifiableSolrParams params = getCommonParams ( ) ; params . set ( "createNodeSet" , nodeSet ) ; return params ; } } public static class SplitShard extends CollectionAdminRequest . CollectionShardAdminRequest { protected String ranges ; public void setRanges ( String ranges ) { } public String getRanges ( ) { } public SplitShard ( ) { } @ Override public SolrParams getParams ( ) { ModifiableSolrParams params = getCommonParams ( ) ; params . set ( "ranges" , ranges ) ; return params ; } } public static class DeleteShard extends CollectionAdminRequest . CollectionShardAdminRequest { public DeleteShard ( ) { } } public static class CreateAlias extends CollectionAdminRequest { protected String aliasedCollections = null ; public void setAliasedCollections ( String alias ) { } public String getAliasedCollections ( ) { } @ Override public SolrParams getParams ( ) { ModifiableSolrParams params = ( ( ModifiableSolrParams ) ( super . getParams ( ) ) ) ; <START_BUG> params . set ( "collections" , collection ) ; <END_BUG> return params ; } public CreateAlias ( ) { } } public static class DeleteAlias extends CollectionAdminRequest { public DeleteAlias ( ) { } } public CollectionAdminRequest ( ) { } public CollectionAdminRequest ( String path ) { } public final void setCollectionName ( String collectionName ) { } public void setAction ( CollectionAction action ) { } @ Override public SolrParams getParams ( ) { if ( ( action ) == null ) { throw new RuntimeException ( "no<seq2seq4repair_space>action<seq2seq4repair_space>specified!" ) ; } ModifiableSolrParams params = new ModifiableSolrParams ( ) ; params . set ( ACTION , action . toString ( ) ) ; params . set ( NAME , collection ) ; return params ; } @ Override public Collection < ContentStream > getContentStreams ( ) throws IOException { } @ Override public CollectionAdminResponse process ( SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse createCollection ( String name , Integer shards , Integer repl , Integer maxShards , String nodeSet , String conf , String routerField , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse createCollection ( String name , Integer shards , String conf , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse createCollection ( String name , String shards , Integer repl , Integer maxShards , String nodeSet , String conf , String routerField , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse createCollection ( String name , String shards , String conf , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse reloadCollection ( String name , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse deleteCollection ( String name , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse createShard ( String name , String shard , String nodeSet , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse createShard ( String name , String shard , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse splitShard ( String name , String shard , String ranges , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse splitShard ( String name , String shard , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse deleteShard ( String name , String shard , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse createAlias ( String name , String collections , SolrServer server ) throws IOException , SolrServerException { } public static CollectionAdminResponse deleteAlias ( String name , SolrServer server ) throws IOException , SolrServerException { } }

Fix:
params . set ( "collections" , aliasedCollections ) ;